The invention relates to a dialysis process for purifying the blood by continuous flow of a dialysate and exchange across the peritoneal membrane.
Heretofore, artificial kidney users have relied basically on two processes for purifying the blood. Hemodialysis involves the circulation of blood through a dialysis machine in which an exchange of toxic metabolites takes place across an artificial membrane outside the patient's body. This process requires the assistance of trained personnel and subjects the patient to dangers of mechanical malfunction due to the fact that blood vessels are involved.
Peritoneal dialysis involves the infusion of a sterile dialysate into the peritoneal cavity and after absorbing waste metabolites, the dialysate is discarded. The process is then repeated until the level of metabolites is reduced to a desired level. This method is commonly referred to as the "Batch" method due to the fact that multiple one or two liter bottles or bags of fresh dialysate solution are utilized which require multiple connections to be made to the catheter inserted in the peritoneal cavity during the dialysis process. The multiple connections made during the course of the dialysis has been thought to be a major cause of the high instance of peritonitis.
Continuous ambulatory peritoneal dialysis offers continuous peritoneal dialysis while still allowing the patient some off time. However, the continuous ambulatory peritoneal dialysis must be done in absence of a machine and multiple bottles or bags of dialysis must be infused daily. Thus, multiple infusions per day requires that multiple connections of bags or bottles to the peritoneal catheter be made. The production of bulk sterile dialysis for the peritoneal process has not been shown to be practical for large scale application particularly for home dialysis.
U.S. Pat. No. 4,311,587 seeks to avoid some of the above problems with peritoneal dialysis by providing a sub-micron filter on line with the fresh dialysate to prevent peritoneal contamination. The system is perambulatory and the bag of dialysate is worn by the patient. The bag may be pressurized by numerous methods and is connected only to the inflow side of the filter. The outflow port of the filter is connected on the other side of the filter so that no peritoneal contaminating source is connected directly to the peritoneal cavity. The system is still basically a batch type system in that multiple bottles or bags of dialysate must be connected to the filter even though direct connection to the peritoneal catheter is not required.
U.S. Pat. No. 4,338,190 discloses a system and process which attempts to avoid the batch process method utilized heretofore in peritoneal dialysis wherein a closed loop peritoneal circuit is provided having a selective membrane across which toxic metabolites are exchanged. A solution is passed on the other side of the selective membrane for maintaining the original concentration of sugar and salt in the peritoneal fluid as the toxic metabolites pass the separator membrane. A concentrate of sugar and salts is mixed at a desired ratio with water making up the dialysis fluid. The conductivity of the fluid may be automatically monitored to adjust the concentration of the fluid during its recirculation. A double peritoneal catheter provides for the inflow and outflow of the peritoneal fluid. However, the peritoneal fluid is constantly recirculated through the peritoneal cavity and the efficiency becomes reduced slightly because of residual toxins which are put back into the peritoneal cavity. The selective membrane is an expensive disposable item which means that the cost of operating the system is high unless the membrane is recleaned. Pumping the peritoneal fluid through the peritoneal cavity is required making it difficult to assure that the patient stays properly distended during the dialysis process. If the peritoneal membrane is not fully distended, it becomes convoluted around the intestines and pockets are formed where the peritoneal fluid can hide. Incomplete circulation then results with decreased efficiency of dialysis. No control is had over the level of peritoneal fluid in the peritoneal circuit. There is no way of replenishing the peritoneal fluid should the circuit run low on fluid or run dry.
U.S. Pat. No. 3,545,438 discloses a batch type peritoneal dialysis method which provides for partially reusing a portion of the dialysis fluid. The spent fluid becomes mixed with fresh dialysate. There is no control or monitoring of the fluid in and out as would allow the dialysate to flow in the peritoneal cavity continuously without dwell time. U.S. Pat. No. 3,707,967, corresponding to German Patent No. 2,149,040, apparently discloses a closed loop dialysis system wherein the dialysis fluid is continuously circulated through the peritoneal membrane. The combination of flow control and monitoring in inflow and outflow lines, and a continuous, cyclic open circuit is not present in the German application. U.S. Pat. No. 3,709,222 discloses a peritoneal dialysis method generally of the batch type. In the U.S. Pat. No. '222, the amount of dialysis fluid entering the peritoneal cavity and the pressure of the peritoneal cavity are controlled by varying the height of a pressure relief chamber. This can be both inaccurate and unreliable, and requires that an attendant be present in order to carry out the process. The cycles involved in the process are rather complicated involving an initial priming cycle which involves the filling of a proportioned chamber, the pressure relief chamber and a return chamber. To begin the process, dialysis fluid s allowed to enter the peritoneal cavity from the pressure relief chamber until the chamber is moved to a lower position which prevents the fluid from flowing. Next, an automatic cycling begins in which the fluid is pumped out of the cavity into the return chamber. Next, an inflow cycle begins in which the fluid is pumped from the return chamber to the proportional chamber which forces fresh dialysis from the proportioning chamber into the pressure relief chamber from where it flows into the patient. Next, there is an equilibrium cycle in which dialysis fluid is drained from the proportioning chamber and fresh dialysis fluid is added. Apparently, during this time, dialysis fluid remains in the cavity. The process then switches back to the outflow cycle in which fluid is pumped from the cavity to the return chamber. French Patent No. 2,371,931 discloses a peritoneal process having a single line used for inflow and outflow. The method includes pumping in a certain amount of dialysate, letting it diffuse for a prescribed dwell time, and removing the dialysate. This is, in essence, an automatic "batch" system.
In the above referenced related co-pending applications, peritoneal dialysis processes are disclosed involving continuous inflows and outflows of fluid using a double catheter in an open loop circuit in which fluid is discarded rather than recirculated. Other aspects of these processes involve using a single catheter open circuit system in which alternating inflow and outflow cycles occur with zero dwell time for the fluid in the cavity. The present invention relates to improvements in the control of these processes and to the control of the osmolality of the fluid in response to the amount of the fluid removed from the patient. The osmolality is continuously adjusted to ensure the basis of the patient.
Accordingly, an important object of the present invention is to provide a continuous cycle peritoneal dialysis system and method which avoid the inherent problems and dangers of a batch type peritoneal dialysis system.
Still another important object of the present invention is to provide a peritoneal dialysis system having a high rate of dialysate exchange providing increased dialysis efficiency.
Still another important object of the present invention is to provide a peritoneal dialysis system and method having a high rate of dialysate exchange and dialysis efficiency in which the osmolality of the fluid is continuously adjusted in response to the amount of fluid removed from the patient.
Still anther important object of the present invention is to provide a continuous-flow single-pass peritoneal dialysis system and method in which the pressure and volume of dialysate in the patient's peritoneal membrane may be monitored and set by the patient in a simple and convenient manner without the need of a medical attendant.